This invention relates to a method and device for attaining a smooth and timely deceleration or stopping of trains which are operated under automatic train control (ATC) systems.
Automatic train control, or ATC, is a known method to control trains in railway systems. Under ATC, a permitted maximum velocity of a train is determined according to the distance to the next train ahead and various condition of each railway section. When the velocity of the train exceeds the specified permitted maximum velocity over a particular section, the ATC brake system is activated and the train is decelerated.
The permitted maximum velocity is occasionally altered according to weather, repair work on the railroads, and other conditions. For instance, the velocity of Tokaido Shinkansens running in the central part of Japan is regulated according to a stepwise reduction of predetermined maximum velocities, i.e. 270 km/h, 255 km/h, 230 km/h, 170 km/h, 120 km/h, and 70 km/h. If the train is required to run at a given limited velocity over a certain section, the permitted maximum velocity is gradually reduced in steps approaching the target limited velocity of the section. If the train has already entered the section where the velocity should have been reduced, it may occur that the velocity is required to be reduced by more than one step. Because of the rather wide range between the steps of velocity, however, an alteration of the train velocity, for example by two steps down from 230 km/h to 120 km/h may result in a sudden braking, making the passengers on board feel a sudden stopping force. The brake system may be deteriorated or have its life shortened as a result of the abrasion or other loads inflicted upon the brake systems.
Therefore, in order to alter the velocity without causing a sudden braking, a person who controls alteration of the maximum permissible velocity must consider the location of the train and reduce the velocity at an appropriate time.
However, it is quite difficult to choose an appropriate time when the railway line is congested, such as during the rush hour. On such an occasion where trains enter, one after another, into a section where alteration of the velocity must be made, the alteration has to be delayed until the line is no longer congested.